1. Field of the Invention
The present invention relates to a method and apparatus for preheating semiconductor chips before bonding them to a lead frame during the manufacture of semiconductor devices.
2. Description of the Related Art
FIG. 1 shows a perspective view of the bonding apparatus for a conventional method of preheating semiconductor devices disclosed in Japanese Published Patent Application 59-104137. In this figure, a bonding apparatus 1 bonds lead frames and semiconductor chips. A magazine 3 feeding lead frames and chips, i.e., the work 2, to a bonding position (not shown) is mounted on the upper side of the bonding apparatus 1. The magazine 3 is open at both ends, and a plurality of shelves for housing the work 2 are installed therein. A preheating apparatus 4 is installed adjacent the bonding apparatus 1 and preheats the work 2. A preheating magazine 5 is mounted on the upper side of the preheating apparatus 4 facing the opening of the magazine 3, is open at both ends, and has a heater 6 therein. A magazine charging mechanism 7 is installed adjacent the entrance side of the preheating magazine 5 and includes a plurality of magazines 8 so that the work 2 can be fed to the preheating magazine 5. The magazine charging mechanism 7 includes a moving mechanism 9 which moves at a right angle to align a magazine 8 with the feed magazine 3 so that the work 2 can be transferred to the preheating magazine 5. A work transfer mechanism 10 ejects the magazine 8 from the magazine charging mechanism 7 and is controlled so that the work 2 in the feed magazine 3 on the bonding apparatus 1 is ejected to the bonding position (not shown) when the preheating time in the preheating magazine 5 reaches a predetermined duration.
In FIG. 1, a driving part (not shown) drives the magazine charging mechanism 7 and moves a magazine 8 to the feed position. Then the magazine 8 is ejected and inserted into the preheating magazine 5 by the work transfer mechanism 10. The heating of the work 2 is started by turning on the electricity to the heater 6. The next magazine 8 is moved to the feeding position by the magazine charging mechanism 7 during heating of the first magazine. Next, after the heating of the work 2 at the heater 6 for a predetermined time, when the work transfer mechanism 10 is driven, the magazine 8 in the preheating magazine 5 is ejected by insertion of the next magazine and is inserted into the feed magazine 3 on the bonding apparatus 1. The aforementioned actions are repeated and the work 2 in the feed magazine 3 is fed to the bonding position (not shown) on the bonding apparatus 1 and bonded.
In the conventional preheating method for the semiconductor parts, a plurality of lead frames and chips in the magazine 8 heated by the preheating magazine 5 are fed to the bonding position from the next feed magazine 3. In the feed magazine 3, since the temperature of the work 2 housed at the downward part of the magazine 8 decreases, the work needs to be heated again at the bonding position. Therefore, there are the problems of not only reduced productivity but also reduced quality caused by movement of the chips relative to the lead frames during movement of the work 2.